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Optimization of a heat assisted air-conditioning system comprising membrane and desiccant technologies for applications in tropical climates

: Safizadeh, M.R.; Morgenstern, A.; Bongs, C.; Henning, H.-M.; Luther, J.


Energy 101 (2016), pp.52-64
ISSN: 0360-5442
Journal Article
Fraunhofer ISE ()
Thermische Anlagen und Gebäudetechnik; Energieeffiziente Gebäude; Kühlung und Klimatisierung von Gebäuden; systems; climates; dehumidification; desiccant dehumidification; optimization

Separating dehumidification and cooling loads in air-conditioning systems has been proven to be a potential strategy to reduce electricity consumption if the dehumidification of air is mostly performed by heat-powered system components. Referring to experimental experiences in Singapore, this paper presents a novel electricity-efficient air-conditioning system consisting of a membrane unit, an evaporatively cooled sorptive dehumidification system (called ECOS system) and a high-efficient conventional cooling unit. The dehumidification of air is performed by a combination of the membrane unit and the ECOS system, and the sensible cooling of air is accommodated by a high-efficiency conventional chiller and in part by the membrane device. In order to find an optimized balance of the three air-conditioning components, an optimization-based simulation approach using a genetic algorithm is developed. The optimization is based on a simple objective function that comprises operating and investment costs. The optimization results reveal that an integration of a relatively large membrane unit, a small ECOS unit and a chiller operating at an elevated evaporation temperature is the most cost effective combination meeting comfort criteria. The resulting optimized combination has potential to save more than 50% of the system's lifetime operating cost compared to conventional systems supplying 100% fresh air.